Originally Posted by drpepper
You can trust that 4 and 8 ohm labels are nominal ratings, not measured ratings.
RS cabs, as tested by Bass Gear are ~10.25 ohms, so 3 would be ~3.4 ohms. TCE knows the actual minimum for their heads and the actual impedance of their cabinets, so they can publish that 3 of their cabinets are supported by their heads.
If the actual safe minimum for a given head is below 3.4 ohms, it would be fine. If 4 ohms is the actual minimum, it may not be fine.
It seems likely to me (so, not something to gamble your money on) that since cabinets can be higher or lower than their nominal ratings, it would be a likely practice to provide leeway in the stated minimum for a head.
That Bass Gear test was not valid. Unfortunately, their tests are kind of a 'published learning curve'.
To the OP, I would not, in any way, run three TC 8ohm cabs with another company's head that is 4ohm minimum. Might be OK, probably will not be.